Why would someone go spend $10.00 on a new tank when they could put a little elbow grease into an old one?
Some people don't have money to throw around, so I find suggestions like that rude.
OP, when I cleaned my hardwater, I just used warm water and a clean rag. It eventually comes off, but you're probably better off with vinegar. Good luck!
It wasn't meant in a rude fashion. I never said to get rid of the old tank. It would make a great quarantine tank. Or breeder. Just not a show tank.But that tank will never have the clarity of new glass. I noticed that when I got my new 20H's last year. And if Petco wasn't having the $1/gallon sale or it was a more expensive tank I wouldn't have mentioned it. I've got 3 20L that have hard water stains. I don't bother cleaning them because i don't want to waste the time since the tanks are still serving their purpose. I'd rather spend that time with my son.
Someday I may clean them up but they will still be utility tanks.